Railroad fissure detector car



JJ w l QHHJT rn .e6 QN m M @u .I .n V 2 m m Q\\2 MMM Q 2 Qun w Y ,m m wvll ./@fw Wm LA L @www n m UJFP? w E m n m l 5 Wm O m \\\M "T a N \\\M m w m 2 a w, m @Wf w w F1 M m m w l May 19, 1953 C, w, MCKEE ETAL 2,639,316

RAILROAD FISSURE DETECTOR CAR Filed Jan. 24, 1949 2 Sheets-Sheet 2 IN N R5.

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Patented May 19, 1953 ches/zer W. McKee 'and Riel-lars W. McKee, ohicago, I ll., assignors to Teledetec'tor, I., Chi

cago, Ill., a. corporation f Delaware Application January 24, 1949, Serial No. 72,382 7 claims. (ci. lis- 183) This invention relates to a method and apparatus for detecting iissures in rail lying in track. Ifhis application is a continuation-in-part of United States copending applications, '5erial No. 628,146, filed ITovemberv 13, 1945; rSerial No. 743,794, led April 25, 1947, 4now Patent No. 2,594,332; and Serial No. 749,166, filed May 20, 1947, now Patent No. 2,602,840. This invention is part of the development disclosed lin issued United States Letters PatentfNo.v 2,338,683, dated November 13, 1945. Two other applications on rail fissure detection are being concurrently led, Serial No. 72, 3B3and 72,384, and the Vfirst few paragraphs of this application are in part explanatory of the development during the past eighteen months.

As explained in the patent, applicants method of fissure detecting turns upon utilizing a small pickup coil having a nonrnagnetic core which in traversing a magnetic leld `does not distort the iield, and consequently, produces potentialv nals faithfully reflecting changes in; direction ancl density o f flu-x the held` As.' explainedy in Eatent No.. 2,I5'38,6 33` the nonmagnetie core pickup coil traversing a true residual` field produces 'a comparatively Weak potential-. sifgnal, thereby necessitating a high. gai-n amplifier. As furtherexplained in cope-riding application, Serial. No.. 628346,. applicants discoveredy that there is a 1art1- eral sustained iicld on each side of the magnet which field is substantially stronger' than a true residual* magnetic el'd. Moreover;- in testing` a lateral sustained' field, non-'hazardous flaw signais' denivedk from surface defectsv are weaker compared to hazaifdous fissure signals than are nant-hazardous flaw signals similarly compared when testing a residual field; that is; the comF parative difference between hazardous and: nonh'sard'ousf, sustained iield ila-W signals is greater than: the comparative difference betweenf hesatdiius4 and non-fhazardous residuali eld iiaw signals. This gieater comparative dii'errence makesv possible` more effective-vdiscrimination: be tween: the two: in. sustained field testing. Appli cents. moved their nonmagneticfcore coilpioltup into.- this. trailing; sustained field and. obtained stronger signals. This made it'possible to lower the gain inthe ampliiier andtherebyf eliminate signals in their-visual. presentationzrneans which were derived from tube characteristics in the Since; the filing. of.Y these applications appliw cents, have. been increesingthe speed! ofy operation of. their, equipment; along the rail. Wlen this was dolle with the equipment dsri'bed'i' the earlier filed copending applications, it was observed that the amplitude of signals from intermal fissures dropped and the amplitude of sig-` nals from harmless surface defects increased-` The magnetometer indicated that the length of the trailing sustained field was abou*4 the same; The applicants concluded that as the speedl of the car increased, the magnetiaing force :reina-in.x ing constant, the tendency of the flux pushed outI along the rail in the trailingsustainediield by the trailing pole was less effective internally of the rail ball Wit-h the result thatpolarizatioriI of surface defects was more compl-ete while polari- :ration of the molecules deep inthe railball Whenethe fissures are., was less complete. @ne might summarize the object of the exploratory step' in rail iissure detect-iony Work by saying that it seeks to produce strong potential signals from haze ardous defects in the rail and Weak o1" no` poterli tial signals from non-#hazardous defects.r It is the comparative strength of the sign-als initially produced i-n the pickup coilby the hazardous and the non-hazardous flux field which is important;- As the speed of applicants car was increased, therefore, this fundamental objective was increasingly defeated., and the applicants* concluded that it Was necessary to further increase themagnetizing force as the speedV of the' car' in'' creased.

The portabie cfa-r shown; in the copendingape plications weighs almost 1,000 pounds and fu-r` ther increasingits Weight greatly impaired its portablity. l\fio 'reover,` a comparison; of the' operating costs of a` portable ssure detector car' operating at two to three miles-an hour withI the operating costs of a non-portable cary open-ating at eight milesy an hour showed that economy in operation favored the latter car, Hence, appliv cants built a non-portabley carv having magnets' showing the same pole arrangement shoivn'win copendfing -applioation-,- Serial No'. 7495166,- but much heavier; these magnets substan polarized the entire rai-l ball at a speed ofv eight toten milesan hour.

ordi to understand th objet''fthis invention, and the discovery which is 'so` Cove-red lill this 'apliati ifi It" sill-3'4 iii/ mind tl'atapplicaiits have used Iio'iim ghtic core coil which efiiteiids over at least side of a rail hall. Thus, iii the Patent" estacas, fn', is sheath 'sin s con having a, vertical @ses erf/sending" tetons' tout eues of thek m11 bau.4 in Figure ci @spending sppiieauon, sei-iai No. t .ainsi t of the rail ball and two smaller coils each across respectively the gauge and eld sides of the rail ball. All of these are nonmagnetic core coils and they do not distort the magnetic flux eld through which they are moving. When applicants put the new car with heavy magnets on test, it was surprisingly successful. It was successful because it found ssures in that portion of the ball of the rail lying inside the joint bars at a track joint. For many years, detectingr equipment has found iissures satisfactorily in the main body of the rail, that is, in that portion of the rail lying between about six inches outside each of the joint bars. Where the rails are thirty-nine feet long and four-bolt, twenty-four inch joint bar is used, approximately eighteen inches at each end of the rail has resisted accurate nssure detection, and where thirty-six inch joint bars are used, there is about twenty-four inches at each end of the rail in which satisfactory fissure detection has not been available. Applicants nonmagnetic core coil has always had more success in detecting fissures in the joint bars than any magnetic core coil. Prior to applicants building the heavy magnets, when applicants nonmagnetic core coil pickup moved over the joint bars, it produced no potential signal unless there was a iissure or a flaw in the rail ball itself. With the development of much heavier magnets, and the nonmagnetic core coils shown in copending application, Serial No. 743,- 794, the pen made a signal as the pickup crossed the ends of the two joint bars in a joint. Applicants were not surprised at this because it has always been known that joint bars and rail braces, particularly in switch'layouts, have magnetic iields about them, and applicants were satisfied with the performance until they discovered that the signal from the ends of the joint bar were of sufficient amplitude when the car was moving at eight to ten miles an hour to substantially impair the ability of the pen unit to record a iissure between the end of the joint bar and the end of the rail. The pen unit is a very indelioate instrument. It writes the full length of a thirty-nine foot rail in two to three inches so that a signal from the end of the joint bar is spaced from the very strong signal derived from the rail joint itself by only one-eighth of an inch, with the result that from a visual standpoint, if the pen attempts to write between the signal from the end of the joint bar and the signal from the end of the rail, an operator is likely to be confused and unnecessary stops for hand checlfing are made. Applicants debated the advisability of supplementing their equipment with the cathode ray tube system disclosed in Patent No. 2,388,683, but rejected this because watching the tube is a very tedious task, necessitating at least one more operator.

The first object ofy this invention is to pick up fissure signals in rail ball lying between joint bars, braces, switch bars, switch heaters, Oilers, or any other magnetizable reinforcements laterally protruding from the side of the rail, without picking up signals from these lateral reinforcements. More specioally, the iirst object of this invention is to devise a coil having a nonrnagnetic core which will not generate a potential signal when threading the magnetic iiuX fields of joint bars and rail braces. This necessitated an analysis of the magnetic flux elds around joint bars, and in Figures 2 and 3, applicants illustrate the magnetic flux eld around joint bars.' The lengthwise coniguration of the lfield ,4 as illustrated in Figure 2 is not clearly understood, but it is believed to be unimportant bccause once the pickup coil has passed over the end of the joint bars, it is apparently moving substantially parallel to the lines of iiux, thereby cutting no flux variations and generating no voltage. A cross sectional configuration of these joint bar flux iields is better understood and is shown in Figure 3. The ilux IB from the joint bar l2 seems to extend above the rail to a point such as lli and is measurable. The flux seems to extend inwardly of the top of the rail in measurable quantities along the dash-dot line I6. This is true on both sides of the rail ball in a joint bar, and it will be seen that there is a sort of tunnel or channel above the center of the rail in which the flux of the joint bar has no appreciable effect. It, therefore, occurred to the applicants that a pickup coil lying inside the vertical planes of the side of the ball, or better, lying inside the diagonal limits i6 and i8 of the joint bar flux iields, would not produce a signal from these fields. Applicants experimented with coils having magnetic cores and coils having nonmagnetic cores. In Figure 3, applicants used a coil having a vertical axis mounted on a nonmagnetic core and having an overall width of about two and one-half inches, the rail shown being a 131 pound rail whose head is three inches across. This pickup coil produced no potential signals derived from iiux iields at the ends of flux bars in moving through a track join'tl` ln Figure 4, applicantsused a magnetic core coil having a transverse, horizontal axis and this produces signals for the ends of the joint bars. Applicants explanation is that the iron vcore formed a shorter path for some of the flux from the ends of the joint bars and pulled the flux directly through it, thus destroying the channel or tunnel between the joint bar flux elds.

The second object of this invention is to adapt the channeling system of applicants copending application, Serial No. 743,794, to a pickup in which all coils are lying inside the joint bar flux eld limits I6 and I8. A feature of this invention is a four-coil pickup assembly, the coils being mounted in alignment transversely of the ball of the rail and each coil connected through a separate amplifier to its own pen unit. Each coil derives potential signals from its own individual longitudinal lane of flux above the rail ball.

Another object of this invention is to provide a more sensitive pickup coil. Applicants earliest nonmagnetic core pickup having a vertical axis had the lower set of windings in a channel having a height of about one-fourth inch. This height, several years ago, was reduced to oneeighth of an inch and in the coils shown in copending application, Serial No. 743,794, the height is but one-sixteenth of an inch. Changing the height of the channels in which the windings lie was a result of using a lighter wire rather than a result of any theorizing on the matter. Some months ago, applicants mounted on the new, nonportable car, a plurality of the small spool coils hereinafter described with the lowermost coil lying in the slot having a height of one-eighth of an inch. With the high strength of the iiux elds obtained by the more powerful magnets, these coils in a test at North Platte, Nebraska, generated a tremendous number of meaningless signals. The present amplifier has a modified form of suppressor on it, see the suppressor of Patent No. 2,388,683, and while the meaningof the signalsgcould be wiped out by the suppressor, iiswe kslemils were' proportionately reduced md in of very smallnssures; sometimes suppressed completely'out. YApplicants, wound in the neldsomenew smallcoils with a channel only 51.2- of an inch high. The test byth'ese coils vwas surprisinglywnccessful, and it v*occurred to 'the applicants that the upper 'windings on a coil .having a vertical aXis'bycutting fui; at a slightly different angle than ythe lower windings of the same coil, may produce voltages whiclimay cancel or 4amplify voltages produced by the lower windings, thus pro'duczing` potential signals of no sigrnficane whatsoever. :[hereupomV the applicents rewoun'd the'coils with 'a still finer gauge of wire,v increasing 'the'numher of turns and these coils have been so'successful that in comparative tests between the three systems of iis'su're detection made shortly before this' writing, itis conceded that the `I'eledetector'car illustrated in Fig- 'ure l, the only car which will Pickup as lowas five per cent to ten per cent fissures in the main body'of the rail, and during the same testing pick up ten` per cent and greater ssuresinside the joint bars.

The following is a verbatim report of a test made4 by the Union PacicRailroad whose employees loperated applicants car, andtherst four lines of the second column indica-te fissures in the ball inside joint bars:

Location of Trans- Y verse Defects From m) of H50 "'EndoIBail 84 Oto 6". 3 (HOW/11.... l

21 13 fois" s 11 to 15%.. e1

. Y 25 to 3D. 0 21th 25%. 7

no 31 to 36" o :ze to 30%... 2

Total. 8.4' 41to 2 Oye: 50%. 14

Total 84 at location. Experiments showfthatwhere the f= pickup "is located'less than eighteen incli'c from the trailing'polomasnet, tlie'cotcntial signal orlo# duced oyj the pickupcoil is of less 'amplitude than the' potential @rial produced by the 'saine coil operated through 'the saine iissure fiux'field'at the saine rate of speed and located three feet behind the trailing 'pole' magnet-` Experiments rhave, also shownha't whe'nthe pickup coil`is `loca ted more than four and one-half feet behind the trailing'poleof the magnet, a weaker potential signal isy produced; A 'noninagnetic :coreY pickup e011' located nl mecen'rer naif of' the trailing sus; tained iield seems' to bev at the most sensitive point for derivinginterna'llssure flux'ields'.'

` `llpplicants recognize that Vthe assertion that the optimuin'point is atthe'inidpointof the' trailing sustained field does` not s'quare'with the theory thatlthevolumof flux' leaving the rail injftlie trailing' sustaii'iel'd field "shuldvary' proportional tothe'fdistalneflom'the trailing Sustained li Moreover, their experiments do not show that positioning the pickup coil at the midpoint of .the trailing Sustained field 'is the optimum point There seems ro :bea-.wide range commencing about one-.fourth ofthe 'length of .the trailing .sustained eld hellind the trailing pole piece Where the strongest .potential signal is produced. Applioants are inclined to think that this .results from the 'fact .that the .flux in the upper Surface of the rail leayes the 'rai-l Afirst and inasmuch as the internal -lissures are usually Adeep within the ball, the .flux whose direction is most affected by' the fissure does not escape from the rail until the aux thereoloovolios loft the-rall- Thoores on this were `.clges-orihe1ci in copending application, Serial .No 7149.15@ y Those ood. Suo-li other obl-@Gto as. mor heroinafter alinear are obtained .in the .embodiment of the invention disolooefl lo the .oooompanylns drawings whel'oloi Eig, l is a perspcctiige .View of applicants newest fissile ,detector oor;

2 is a 'side eleyation of a track joint illus-y trating sonic of the lines of iiux in the air around e joint bari Fig. 3 is a view in section of the flux eld taken on the lino. 3.-,3 of Fla 2;

Fig. 4 is a view in section taken on the line of Fls- 2 lout Showing how o oiokup coll having an iron coro .distorts the fields .of the joint bars:

Figs. 5I 6, 7 and 8 are views partially in section showing other mosnotloablo. reinforcements protrudne laterally of a rail. namely. rail braces. a switch point and switch bar, an oiler, and a rail heater, rosllcotitoly;

Fle- 9 is o .Sohometio illustration of ooplioollls improved pickup coil moving through a switch point together with a greatly lonshonod Section of tooo. illustrating the. typo of Signal rooivod from @con of applicants small coils es they more into the field hetween the switch point and the rail curving away from thev main track, the ourvaturcof this roll boing exaggerated;

Eig. 10 is a plan View of applicants pickup assembly together with schematic illustration of the electrical connections between each coil and its pen unit. figure also shows in full socle. o portion of the'. tape as. Written by the ooo unit;

Fig. 11 is a side elevational View, partly cut away of applicants pickup assembly and small spool coil; and

l2 is a perspective View of one of appli.- cants small spool coils..

Continuing to refer. toI the drawings., in Fig. l, the numeral 2l)i identifies a iis-sure detector car supported on trucks 2,2 and 2 4". A. heavy magnet assembly 26 is suspended between the two wheel-s of; each side and pickup assembhT t8 is positiched between the wheels ovfthe truck 22. The wheel fili. is :nado ciV nonmagne'tic material. The forward or cab end. oi the car. is to the.A left and the. operators rooni is to the right. The engine room is located between the calo and the operators room and the driving elements for the car and the generators forA energizingv the magnets and hand check electrodes need not be describedA The pen and tape unit need not be described. Applicants have been using mechanical trains for synchronizing, the pen unitv with the 'forward speed of thecar but shortly expect to. utilize a pair of Selsyn motors, onedrivingly connectedfto a wheel. aile'an. the other to the peri unit, an arrangement somewhat similar to"thatemployedin applicants original' car shownin Fatent No. 2,388,683.

Referring to Fig. 10, applicants pickup assembly 2S consists of a block 34 of nonmagnetic material having five through holes 36, 33, li, l2 and lid positioned as illustrated. This pickup assembly 28 is designed for a 131 pounds railv 46 which has a ball Width oi three inches. The gauge and field sides of the rail are indicated by the numerals 'i8 and 5i? respectively. A plate 52. of nonmagnetic material is fastened over the bottom of the block 3ft, see Fig. ll. Returning to Fig. 10, the outside edge eli of the hole i2 is spaced from the gauge side of the rail ball d8 by a distance of T36 of an inch; and the outer edge 5t of the hole 35 is similarly spaced from the field side 5G of the rail ball. The four holes 36, 38, du and d2 are in alignment and equally spaced from each other. The hole Il is centered over the rail ball. The pickup assembly is, independently suspended from the car 20 in such a way that the center of the assembly, particularly the hole 46, is positioned directly over the center of the rail ball. This is done by a suspension rig which performs this function whether the car is moving on straight or curved track and which need not be shown and described as it forms no part of this invention.

Applicants flux responsive means are coils wound on nonmagnetic cores. Applicants call them spool coils and they are all identical in the number of windings, the size of the wire used, the diameter of the coil core itself, and the outside diameter of the coil. One coil for generating signals from the joint, however, is inversely mounted with respect to the other four.

Examining now one of these coils, referring to Fig. 11, the numeral 58 identies a block of nonmagnetic material in the circumferential surface of one end of which is cut an annular channel 60. The lower edge of this channel is spaced from the plate 52 by el@ of an inch and the channel width or height is ele of an inch. Spaced from the upper side of this channel by one-half inch is a like sized channel 62. Channels Sli, 65, and (iii having a depth of about slsof an inch are cut in the cylindrical surface and one end of the spool block 58 so as to form passageways connecting the two channels Si! and 62 to each other and to one end of the spool. i

A large number of turns of ne insulated wire are wound in the channel tu and their lead ends are carried up the channel 6d where a similar number of turns but in the opposite direction, are wound in the channel 52. The windings in the channels 0 and 62 are series connected and the two lead conductors are carried up to the end of the spool and out where they are given the designations 'i0 and l2.

Four spool coils lli, it, i8 and dil are dropped into the holes 3K5, 38, di) and d2 ofv the pickup block 3d, see Fig. 10, with the channel 60 down. In this position, the coil in the channel 6B constitutes the fissure iiux responsive means. This coil generates the potential signals from the fissure iiux fields. The opposed Winding in the channel 62 serves to cancel out non-significant potential signals generated by large elds emanating from equipment on the car, although in the Very strong abnormal fields in the rail ball, this upper coil may serve to partially cancel the signal derived by the lower coil.

'I'he pickup assembly 28 is positioned ideally at a height above the rail of about 1/8 inch, as illustratedin Fig. 11. Y

A rail joint spool coil 32 is identical with the other coils but is inversely mounted in the hole 44, as illustrated in Fig. l1, so that the coil in the channel im is close to the top of the pickup assembly 28 and the coil in the channel 62 is spaced from the top of the rail by almost 1%; of an inch. The coil in the channel 52 acts as the potential signal producing element and it is spaced at a much greaterdistance above the rail joint. Because the intensity of the flux field varies proportionately, inversely with the distance of the pickup coil from the rail, the signal produced in the coil in the channel 52 of the rail joint spool 82 will have much less amplitude than the signal produced in the rail joints in the other four spool -coils with the result that the rail Ajoint signal will be of shorter duration and more precise, which is desirable.

The spool coils i4, lt, 'i8 and 8l! are each channeled through their own amplifiers 8A, S6, 83 and 9E), and the output of these amplifiers is respectively delivered to pen unit assemblies d2, 94, 9e and 98. 'I'hese amplifiers and pen units need not be described. The rail joint spool core 82 is separately channeled to amplifier lill) and the output of this amplifier leads to pen unit 02.

Referring now to that portion of Fig. 10 illustrating a portion of tape produced by applicants pickup assembly, the numeral |04 identifies the rail joint signal path, 06 the gauge signal path, 98 the gauge center signal path, il@ the field center signal path, and H2 the field signal path. It will be observed that the rail joint signal H4 is of shorter duration than the rail joint signals produced by the other four spool coils. Note also that each coil may produce a signal without any of the otherl coils receiving any signal. Note signals H6 and IIB. The importance of applicents small coils closely spaced can be appre-v ciated by understanding the significance of these signals H6 and lill. Their significance is that they have no signicance. A study of the rail at the points where the flux 'fields produced these signals llt and H8 will disclose no nssure. Instead, the rail at these points will disclose some slight aberration which is of no significance `from the standpoint of a dangerous fissure. This boils down to saying that applicants multiple coil pickup is discriminatory between significant potential signals and non-signiiicant potential signals in that two signals transverselyvaligned on the tape such as il and l22 must occur to justify stopping the car to perform the time-con suming hand check. The only signals. shown on the tape in Fig. 10 that justify stopping the car to perform a hand check are signals 12) and |22. Applicants do not discount the fact that one spool coil mightproduce a signal il' as a result of passing. through a very smallr fissure vilus; field, but applicants apparatus picks up fissures as small as live per cent of the ball head and when such fissures have been found in the past, they have invariably appeared in two adjacent pen unit signals. i

The signals l26 and I2$ would justify a stop if unexplained. Along the gauge and field sides of a rail are to be found frequently shells, flaws and spalled-out spots which are harmless, and the operator watches for these. It happens that they lie almost universally close to the gauge and field edges, and consequently, byA having four aligned coils, the failure of either the gauge center or the field 'center coils to record a'signal is almost conclusive evidencey that signals produced by the gauge or field coils-alone' are not aesa'aie derived from dangerous aws. Where one of the center pens records `a signal -simultaneously with afield or gauge pen, if the operator cannot see from his seat inA the ycar a-shell orflow or `burn or .spelled-out spoty he will stop 'the car for a hand check.

It is seen, therefore, that lit is the 'transverse alignment of the small Vcoils in applicants. .pickup assembly which provides .a .method of discriminating between harmless flaws and dangerous fissures during the exploratory step. This is solely the result of the .transverse alignment ci the coils and of the pens. .Oene :could obtain much the `same vvresult `by staggering .the coils along the rail and then by.'correspondingly staggering the pens of. the. tape. A tapefoi .like sig niiicance and equally readable would result. But this arrangement of coilsis vnetto .be confused .with the theoryfof anyzstaggered arrangement of coils such .as that shown inFig. 6 of co.- pending application, Serial .-No. 743,749. Theoretically, the staggered coils-.in this -application produce three successive. signals from `a transverse fissure and produce `on the tape three successive signals-successive4 in point ofv time. However, visibly, the three signals would be simultaneous because the spacing ofthe coils longitudinally ofthe -railfromeach other isonly a matter of three or fourinches, and the spacing of signals on the `tape derived from this length oi' railwould not be perceptible. l 1

Applicants method ofl distinguishing various typesrof flux from each other during-the exploratory step turns'upon-producing a Aplurality of .signals ,simultaneously from the'fsame 'transverse portion of a rail, in conjunction with the operators watching the rail. The narrowness of the coils as measured transversely of the rail is important. The ux ields foi the railv are 'divided into four longitudinal channels, each of which channels is traversed by, one Aflux :responsive means, connected to its own ampliiier and :its own pen unit, Vthepen units being so related that they will show simultaneously produced signals.

Returningnow .to Fig. fl, the pickup coil 28 is located aboutl four feet behind the trailing pole of the magnet 26. In the trailing sustained field generated by these, magnets, this Aposition Yis slightly more thanhalipi thelengthpi the trailing sustained yfield generated 'by 'the magnets when thecar is moving ateiglit or nine milesan hour. Byincreasing the capacityoi thefmagnets a drop in the length of the-trailing sustainedfeld due lto increasing the speed of the car, vcan be compensated for. -When a lllpound rail is saturated, applicants -iind that lthe length of the trailing sustained ield is approximately six or seven feet. Undoubtedly, there is some magnetism in the rail further back from the trailing pole, but it is not perceptible, it has become truly residual magnetism. The pickup coil should be positioned some place in the central half of the trailing sustained held. Its exact position will depend upon other elements of the car. A pickup coil positioned at point 29 is too close to the trailing sustained iield and is not believed to be traversing lines of flux from deep inside the rail which are greatly affected by an internal fissure.

Figure 9 illustrates the type of signal that may be received by applicants apparatus moving through a switch point. The purpose is to show that applicants apparatus can detect fissures in switch points. The signals |30, 132, |34 and |36 are the maximum signals produced by applicants coils. As each coil passes over the joint between the switch point andthe rail, it may produce a signal as shown. Ordinarily, no signal is produced because a pickup coil moving longitudinally of the rail does not produce a signal for a longitudinal separation, even for a joint suc-h as that between a railand a switch point. The only time that a vertical or horizontal split head produces a signal is when it has a transverse component and fortunately a iissure that stems from a longitudinal split develops a transverse component while it is still very small. The separation between the rail and` the switch point illustrated in 9 would probably produce the signals shown on the tape because the separation has a denite transverse component. In actual switches, however, the curvature vof the rail {33 is not nearly so sharp,w-the lateral deviation being a fraction of an inch per linear foot, with the result that applicants pickup coil vmoving through a switch point in Whchneither the rail nor the switch point contains any internal fissures will produce no signalsfat-all. It follows that applicants coils will readily write ssures in the switches.

In the switches, applicants improvement of the four transversely aligned coils all lying of an inch inside the edges of the rail ball is very valuable because vthe switch points are connected by 4cross arms'and fthe cross arms are fastened to the switch lpoints by protruding steel anges. All of these laterally protruding elements gencrate flux fields, but being substantially lower than the top or" the -rail ball, the tunnel or channel of flux above the central -part of the ball and close-to its surface, which flux is substantially unaected by the fiux lields of these laterally -protruding elements, remains.- In most switches, the rails such as 138 are supported by rail braces. Then too, as illustrated in Fig. 8, there is irequently positioned adjacent the side of the rail web opposite the switch point, a heater, which alsosets up its own magnetic flux field.

Applicants pickup coil successfully detects iissures in a rail ball which-is surrounded by all of this equipment. Y At thepresent time the only portion of a railthat remains untested is the frogs of switches and Crossovers. The only place where applicants raise their pickup coil, at the present time, so as to discontinue flaw detection work as the car moves-along the rail, is at these frogs.

There is-one frog on one rail in each switch and,

of course, four frogs `at each crossover.

The'cross'section shown in Fig. 7 is schematic.`

An oiler is a bar lying along one side of a rail ball which can be raised and lowered and in so doing smears the iangeside of the rail ball with oil; vTheYoiler-sjprotrude from the side of the rail by a distance slightly greater than that of the joint bars.

Referring to Fig. l0, the numeral I 40 identiiies a bell which is sounded by the closing of a relay :i2 in a bell circuit containing the armatures |44 and MB of a pair of relays M8 and 159. The relays M8 and itil are respectively connected to the circuit from the eld center coil le and the circuit of the gauge center coil i8. When a potential signal is received by both of these circuits at the same moment, both armatures Mii and Hit are closed, thereby ringing the bell. This bell system is to assist the operator. All signals including those from very small iissures ordinarily produce potential signals in both of the center coils, and it is important that an operator never overlook two laterally aligned signals on the two center lines on the tape. Also the bell will serve as a check on any deficiencies of the two center line pens. It is true, however, that'a skilled operator does not need this bell arrangement. Each pen unit clicks when functioned. When a joint is crossed, ive pen units click simultaneously. When traversing the main body of the rail only rarely does more than one pen unit click at the same moment. A skilled operator can tell by the sound Whether one or two pen units click.

Having thus described our invention, what we claim is:

1. Rail car ssure detection apparatus comprising a car supported by track wheels, a plurality of pickup coils each Wound on a vertically disposed nonmagnetic core and suspended above the rail ball, said pickup coils being non-overlapping longitudinally and transversely over the rail b all so that each will examine exclusively a longitudinal path of flux elds above the ball, and a separate amplifier connected to a separate visible signal producing means with the input oi each amplifier connected to each pickup coil.

2. Rail car iissure detection apparatus comprising a car supported by track Wheels, a plurality of pickup coils each wound around a vertically disposed nonmagnetic core and suspended over the rail ball, said coils being non-overlap ping longitudinally and transversely and aligned transversely over the rail ball With all coils lying inside vertical planes containing the side walls of 'the rail ball, a separate amplifier connected to each coil, and a pen unit connected to each am plii'ier, said pen units being in transverse align ment over a common movable tape.

3. Rail car fissure detection apparatus comprising a car supported by track Wheels, four pickup coils suspended over the rail ball, each coil being Wound around a vertically disposed nonmagnetic core and each having an outside diameter of approximately one-hali inch with a height of approximately one-thirty-second of an inch, said coils being non-overlapping longitudinally and transversely and aligned transversely over the rail ball with all coils lying inside vertical planes containing the side walls of the rail ball, a separate amplifier connected to each coil, and a pen unit connected to each amplifier, said pen units being in transverse alignment over a common movable tape.

4. A method of detecting internal fissures in rail ball lying in track which comprises the steps of progressively energizing the rail ball to form iiux fields thereabout, of moving simultaneously a plurality of small, independent pickup coils in sideby-side transverse relationship to the rail through the ux elds above the rail, of moving a like plurality of small, independent pickup coils each in bucking-out relationship in the circuit of one vof the associated coils and in side-by-side relationship at a point immediately above the iirst set of coils, and of presenting simultaneously and independently potential signals generated by each pair of coils in sensibly apprehensible form.

5. Rail car fissure detection apparatus cornprising a car supported by track wheels, means for longitudinally magnetizing a rail suspended from the car, a plurality of small pickup coils suspended from the car, said coils being non-overlapping longitudinally and transversely aligned over the rail ball so that each will examine exclusively a longitudinal path of residual flux elds above the ball, and a separate ampliiier connected to a separate Visible signal-producing means with the input of each amplifier connected to each pickup coil.

6. The apparatus of claim 5 wherein the visible signal-producing means consists of separate pens each associated with one amplier and all writing on a single moving tape.

7. In rail iiaw detecting apparatus, the combination oi' means for progressively energizing a rail to establish characteristic magnetic conditions in the vicinity of flaws, and other characteristic magnetic conditions in the vicinity of -surface defects, a detector unit comprising at least three detectors for inductively locating said conditions, a plurality of amplifiers, one associated with each detector and recording means including a moving tape and a plurality of recording pens, one associated Witheach amplifier and detector, for making parallel line records on the tape in response to thedetectors, said. detectors being 'A spaced apart in lateral alignment, and each including a coil in close magnetic coupling with a speciiied longitudinal portion of the top of the rail head, said detectors being of such size and inductive strength, and so arranged that there is substantially n0 overlapping between adjacent longitudinal portions of the top of the rail head magnetically searched by said laterally spaced coils, the width of each detector being less than one-fourth oi the width of the rail head,

Meshv May i6, o 

